Turbine method and system



i E. L. KUMM TURBINE METHOD AND SYSTEM Dec. 3 1957 Fiied Nov. 5,

TURBNE METHOD AND SYSTEM Emerson L. Kramm, Pacific Palisades, Calif.,assignor to Propulsion Research Corporation, Santa Monica, Calif., acorporation Application November 5, 1956, Serial No. 620,492

11 Claims. (Cl. 121-1) The present invention relates to gas or vapordriven turbines of the liquid piston type. The invention is moredirectly concerned with an improved method and system for enabling sucha turbine to be operated with its inlet driving gas or vapor establishedat a relatively high temperature for increased operational eliciency.

Copending application Ser. No. 605,801, filed August 23, 1956, in thenames of Emerson L. Kumm and Wilbur D. Crater, entitled Gas Turbine,which was assigned to the assignee of the present application, disclosesand claims a liquid piston turbine which includes a series of vanes thatare arranged to rotate about a fixed hub in response to a high pressureinlet gas or vapor, this gas being introduced between successive ones ofthe vanes through an inlet port in the hub.

The driving gas introduced into the turbine of the copending applicationis trapped between the vanes by a rotating body of liquid which isreferred to as a liquid piston. The liquid for this piston is alsointroduced through the stationary hub. The liquid piston surrounds thevanes and rotates with the vanes. The outer casing of the turbinedescribed in the copendingapplication is permitted to rotate freely ineccentric relation with the rotation of the vanes. This eccentricrelation of the vanes and casing allows the driving gas to expand in theturbine and to do work on the vanes and on the liquid piston. Thisexpansion of the driving gas causes the vanes to rotate about thestationary hub. The driving gas is subsequently discharged through anoutlet or exhaust port in the hub.

As pointed out in the copending application, turbines of the typedescribed in the preceding paragraphs are capable of generating drivingshaft power from the high pressure inlet gas, and of generating thispower more efficiently than most other types of gas turbines, this beingespecially evident in the smaller units and in units having relativelylow rotational speeds.

The gas consumption of the liquid piston turbine described abovedecreases tor a particular output power when the temperature of theinlet driving gas is increased. Therefore, the eiliciency of the turbineincreases with an increase in temperature of the inlet driving gas. Itis evident, therefore, that from a standpoint of elliciency, it is moredesirable to establish the inlet temperature of the driving gas at ashigh a value as possible. The maximum temperature of the gas is, ofcourse, limited by the maximum temperature under which the mechanicalcomponents of the turbine will operate, and also by the maximumtemperature conditions under which the liquid piston will exhibitrelatively low vapor pressure and will retain its liquid properties.

Alloy steels and other materials generally used in turbine constructionwill operate in extremely high temperature ranges, so that the upperlimit of temperature operation of the turbine is dictated by the liquidpiston, for practical purposes, rather than by the other mechanicalcomponents.

tates atent V* 2,815,003 Patented Dec.. 3, 1957 ICC Water is not asatisfactory substance for the liquid piston when high temperatureoperation is desired. This is because a liquid piston composed of waterexhibits inordinately high vapor pressures at elevated temperatures.Oil, likewise, is not a suitable substance for the liquid piston in thehigher temperature ranges. This is because most oils form carbondeposits and also partially vaporize at temperatures above 500 For thesereasons, it is clear that a liquid piston formed of usual known types ofoil is not satisfactory for desired operation in the high temperaturerange of, for example, around 1,000" F. l

Mercury is a possible substance for use as the liquid piston in suchhigh temperature operation. However, mercury at the present time isextremely expensive. Moreover, mercury vapor is toxic and thereforeextreme care must be exercised in the use of this substance.

The problem resolves itself, therefore, into the requirement for asubstance that may have a liquid form at normal ambient temperatures toenable it to be conveniently introduced into the turbine, and yet asubstance that will retain its liquid properties in the elevatedtemperature ranges and exhibitrelatively low vapor pressures. Thesubstance, in addition, must not be materially corrosive and it must becapable of being; easily removed from the interior of the turbine casingat the end of each operation of the turbine.

A salt mixture is presently known which becomes molten at a relativelylow temperature (around 300 lil), and which exhibits negligible vaporpressure for temperatures up to at least l,000 F. This salt mixture hasessentially the following composition:

Percent, by weight Sodium nitrite (NaNO2) i 40 Sodium nitrate (NaNO3) 7Potassium nitrate (KNO3) 53 solution, therefore, becomes more and moreconcentrated and passes from a solution to its molten state withoutlosing its liquid properties as the temperature of 300 F. is approachedand passed. The molten salt mixture then continues to function at thehigh temperatures as the liquid piston, and the molten salts desirablyexhibit negligible vapor pressure at these high temperatures.

At the end of an operation of the turbine, the turbine may be permittedto cool down allowing the salt mixture to crystalize and to be depositedon the internal surfaces of the turbine. However, the crystalizedmixture can readily be washed out by water and formed into a solutionthat may be stored and held in readiness for the next cycle of operationof the turbine. Alternately, the salt mixture can be washed out of theturbine by water at the end of an operation of the turbine before it hascrystalized.

l The salt mixture referred to above is ideal for the purpose of thepresent invention because it exhibits a relatively low melting point(about 300 E), because it is readily soluble in water, and because ithas negligible vapor pressure at the elevated temperatures (of the orderof 1000 F.). Also, this salt mixture is suitable because of itsnon-corrosive properties, and also because 3 it will continue to exhibitliquid properties as it passes from its dissolved state in solution toits molten state as the temperature is increased.

It is evident, however, that the process and system of the invention isnot limited to the particular substance or mixture described above, andthat other mixtures and substances exhibiting similar favorablecharacteristics can also be used.

The various features and advantages of the process and system of thepresent invention will be readily understood from the following detaileddescription, when read in conjunction with the accompanying drawing.

In the drawing, which is to be regarded as merely illustrative Figure 1is a sectional somewhat schematic view of a liquid piston turbinesimilar in some respects to the one disclosed in the copendingapplication referred to previously, and which turbine has been modifiedto incorporate the improved system and method of the present invention;and

Figure 2 is a cross-sectional View, substantially on the line 2 2 ofFigure l, showing the rotatable turbine vanes together with theencircling liquid piston, and also schematically showing the entrappedgas between successive ones of the vanes.

The turbine illustrated in the drawing includes the stationary hollowhub which is supported on any suitable base (not shown). A series ofradial vanes 12 are supported by a pair of spaced end brackets 14 and16. The resulting unitary vane assembly is supported for rotation aboutthe stationary hub 10 by bearings 18 and 20. A drive-shaft 22 is formedintegral with the bracket 14 and extends through one end of the turbineco-axial with the axis of the hub 10.

An outer casing 24 is freely rotatable about an axis spaced from andparallel to the axis of the hub 10. The casing 24, therefore, isrotatable in eccentric relation with the vanes 12. The casing issupported for such eccentric relation at one side by a bearing 26 whichis positioned between it and the hub 10. The casing is supported on theother side by an eccentric disc-like member 28. The disc-like member 28is stationary and the shaft 22 is rotatably mounted in this stationarymember by means of a bearing 30. The casing 24 is rotatably mounted onthe disc-like member 28 by means of a bearing 32.

The construction described above permits the vanes 12 and thedrive-shaft 22 to rotate about the axis of the hub 10, and it alsopermits the casing 24 to be freely rotatable in eccentric relation withthe vanes about a second parallel axis.

The driving gas or vapor is introduced to the unit through a feed line40. This feed line extends into the hollow hub 1t) and along that hub toan inlet port 42 leading to the interior of the casing 24. The drivinggas is subsequently exhausted from the turbine through an exhaust oroutlet port 44 in the stationary hub 10, and then through the interiorof the hub to a suitable exhaust line (not shown). The exhaust line maybe appropriately coupled to the left hand end of the hub in Figure 1.

A liquid salt solution is introduced to the turbine through a pipeline50. This latter pipeline extends into the hollow hub 10 and along thehub to an inlet port 52 also leading to the interior of the casing. Thislatter inlet port is angularly positioned on the periphery of the hubbetween the inlet port 42 and the exhaust port 44.

In the manner fully described in the copending application referred toabove, and when a liquid is introduced through the line 50 to theinterior of the casing 24, a driving gas introduced through the inletport 42 is trapped between successive ones of the vanes 12 by the liquidpiston resulting from the introduction of the liquid. This liquid pistonis represented by the area 54 in Figure 2, and the introduced drivinggas is represented by the stippled area 56 in that figure.

As clearly shown in Figure 2, the driving gas expands 4 doing work onthe vanes and on the liquid piston, this being permitted by theeccentric relation between the axis of rotation of the casing 24 and ofthe vanes 12. The work done by the expanding driving gas causes thevanes 12 to rotate about the hub 10 and produce a driving torque on theshaft 22. The expanded driving gas then escapes through the exhaust port44.

It will be noted that the liquid piston 54 rotates with the vanes 12,and that the casing 24 is allowed to rotate with the liquid piston so asto reduce friction losses between the casing and the liquid piston. Thisconstruction is described in the copending application referred toabove.

To adapt the turbine for operation in accordance with one embodiment ofthe present invention, an overow sump 69 is formed in the hub 10. Areservoir 62 also is provided, and a pipeline 64 connects the sump tothe reservoir. A water inlet line 66 extends from the reservoir to asuitable water source, and a valve 68 is provided in that line tocontrol the introduction of water to the reservoir.

An electrically operated pump 70 has its inlet coupled to the reservoirthrough a pipeline 72. The outlet of this pump is coupled to a pipeline74, and a solenoid-operated valve 76 couples the latter pipeline to thepipeline 50.

The pump 70 is connected to a source of direct voltage 78 through a pairof electric leads 80, and a manually operated start-and-stop switch 82is included in circuit with one of these leads.

An examination of Figure 2 will reveal that the liquid piston justtouches the surface of the hub 10 at a point adjacent the liquid inletport 52 and that the remainder of the periphery of the hub is contactedby the entrapped gas in the area 54. This fact is taken advantage of incopending application Ser. No. 576,184 which was filed April 4, 1956, inthe name of the present inventor and which was assigned to the presentassignee.

In that application, a sensing element is positioned on the periphery ofthe hub adjacent the liquid inlet port, and that element is used tocontrol the flow of the liquid to the turbine. The control is such thatthe proper amount of liquid is maintained in the casing for the liquidpiston in the presence of the continual escape of the liquid.

The present invention utilizes the control described in the lattercopending application, and such a control is indicated by the block 84.The solenoid control portion of the valve 76 is connected to the sourceof direct Voltage 78 through the sensing element 84. In the manner fullydescribed in the copending application, when the element is in arelatively cool condition because it is covered by the liquid piston,the solenoid valve is deenergized and closed. However, when thetemperature of the sensing element rises because it is no longer coveredwith liquid, the sensing element closes. This closure of the sensingelement energizes and opens the solenoid valve 76 so that more liquidmay be fed into the turbine. This llow continues until the liquid pistonhas been sutiiciently replenished so that it once again covers thesensing element 84. The sensing element then cools down and opens. Thisopens the circuit to the solenoid valve 76, and the valve closes andterminates the ow of liquid to the turbine.

In practicing the present invention, the salt solution is placed in thereservoir 62. When the turbine operation is first initiated by theintroduction of hot driving gas through the feed line 40, thetemperature of the sensing element 84 immediately rises to thetemperature required to cause it to close and energize the solenoidvalve 76. The valve, therefore, opens and a suicient amount of the saltsolution is fed into the turbine to form a liquid piston. When theliquid piston covers the element 84, the flow of liquid through thepipeline 51B is terminated. The hot driving gas introduced through theline 40 is now trapped between the vanes 12, and the turbine is rapidlybrought up to speed in the manner described in the copendingapplications referred to above.

The excess salt solution iiows out the exhaust port 44 and back throughthe hub to be accumulated in the sump 60. The solution then Hows back tothe reservoir 62 through the pipeline 64 for recirculation.

Now, as the internal temperature of the turbine increases, the water orother solvent of the salt solution is vaporized o, and the solutionbecomes more and more concentrated. The vapor escapes through theexhaust port 44. Gradually, and as the internal temperature iscontinually increased, the liquid piston is transformed from a solutioninto molten salts. The sensing element 84 continues to control the feedof the liquid piston, and it causes more of the solution to be fed tothe interior of the turbine whenever depletion of the molten saltsrequires it.

When the operation of the turbine is terminated, it is allowed to cooldown, and the salts crystalize within the casing. To remove the salts,it is merely necessary to cause the pump 70 to circulate the solutionfrom the reservoir 62 through the system. It is evident that more watermay be added to the solution by the valve 68 whenever additional solventis required. Also, the solenoid valve 76 may have a manual control, orby-pass, to permit the flow of the solution through the pipelines 74 and50, at this time and when the valve 76 would normally be closed.

The invention provides, therefore, an improved method and system whichpermits a liquid piston for a turbine to be conveniently formed andcontrolled throughout an extremely wide temperature range. Moreover, themethod and system of the invention provides for a liquid piston whichallows an extremely high temperature driving gas to be used forincreased overall efficiency of the assembly.

Although the now preferred embodiment of the present invention has beenshown and described herein, it is to be understood that the invention isnot to be limited thereto, for it is susceptible to changes in form anddetail within the scope of the appended claims.

I claim:

l. In a liquid piston turbine which comprises a plurality of radialvanes mounted for rotation about a central axis, and an outer casingenclosing the vanes, the combination of: a liquid piston comprising asalt solution included in said casing; and means for introducing a gasbetween successive ones of said vanes to be entrapped between said vanesby said solution, and said gas having a suiciently high temperature toconvert said salt solution to a liquid salt.

2. In a liquid piston turbine which comprises a plurality of radialvanes mounted for rotation about a central axis, and an outer casingenclosing the vanes and rotatable about an axis parallel to and spacedfrom said central axis, the combination of: a liquid piston comprising asalt solution included in said casing and rotatable with said casing;means for introducing a gas between successive ones of said vanes to beentrapped between such ones by said solution so that expansion of saidgas produces rotation of said vanes, and said gas having a sufficientlyhigh temperature to convert said salt solution to a liquid salt; andmeans for exhausting said gas from between said successive pairs of saidvanes upon the expansion of said gas and the performance of work therebyon said vanes.

3. In a liquid piston turbine which comprises a plurality of radialvanes mounted for rotation about a central axis, and an outer casingenclosing the vanes and rotatable about an vaxis parallel to and spacedfrom said central axis, the combination of a liquid piston comprising asalt solution included in said casing and rotatable with said casing;means for introducing a gas between successive ones of said vanes to beentrapped between such ones by said solution so that expansion of saidgas produces rotation of said vanes, said gas having a sufficiently hightemperature to convert said salt solution to a liquid salt; a reservoirfor said salt solution; means including a pump for circulating the saltsolution from the reservoir to the interior of said casing to replenishsaid liquid piston and for returning excess solution to said reservoir;and means` for exhausting said gas from between said successive pairs ofsaid vanes upon the expansion thereof and the performance of workthereby on said vanes.

4. The combination set forth in claim 3 `and which further includesmeans for controllably introducing water to said reservoir.

5. The combination set forth in claim 3 and which further includesautomatic means for controlling the introduction of the solution fromsaid reservoir to the interior of said casing.

6. In a liquid piston turbine unit which comprises a plurality of radialvanes mounted for rotation about a central axis, and an outer casingenclosing the vanes, the 4combination of: a liquid piston included insaid casing and comprising a salt mixture of sodium nitrite, sodiumnitrate and potassium nitrate in solution; and means for introducing agas between successive ones of said vanes to be entrapped between suchones by said solution, said gas having a sufficiently high temperatureto convert said solution into liquid salts.

7. The combination deined in claim 6 in which said salt mixture is, byweight, essentially 40% sodium nitrite, essentially 7% sodium nitrate,and essentially 53% potassium nitrate.

8. The method of driving a series of radial vanes about a central axiswhich comprises surrounding the vanes with a salt solution, andintroducing a gas between successive ones of said vanes of suicientlyIhigh tempenature to convert the salt solution lto la liquid salt.

9. The method of driving a series of radial vanes about a central axiswhich comprises surrounding the vanes with a salt solution comprising asodium nitrite, sodium nitrate and potassium nitnate; and introducing agas between suc cessive ones of said vanes of sufiiciently hightemperature to convert the salt solution into liquid salts.

10. The method of driving a series of radial vanes about a central axiswhich comprises surrounding the vanes with `a salt solutionsubstantially comprising, by weight, 40% sodium nitrite, 7% sodiumnitrate and 53% potassium nitrate; Iand introducing a gas betweensuccessive ones of said vanes of =a sutliciently high temperature toconvert the salt solution into liquid salts.

11. The method of causing rotation-a1 motion of `a series of drivingelements which comprises surrounding the elements with a solution of atleast one soluble substance, and introducing a driving uid betweensuccessive ones of said elements of suiciently high temperature toevaporate the solvent from said solution land to liquefy said substance.

No references cited.

3. IN A LIQUID PISTON TURBINE WHICH COMPRISES A PLURALITY OF RADIALVANES MOUNTED FOR ROTATION ABOUT A CENTRAL AXIS, AND AN OUTER CASINGENCLOSING THE VANES AND ROTATABLE ABOUT AN AXIS PARALLEL TO AND SPACESFROM SAID CENTRAL AXIS, THE COMBINATION OF: A LIQUID PISTON COMPRISING ASALT SOLUTION INCLUDED IN SAID CASING AND ROTATABLE WITH SAID CASING;MEANS FOR INTRODUCING A GAS BETWEEN SUCCESSIVE ONES OF SAID VANES TO BEENTRAPPED BETWEEN SUCH ONES BY SAID SOLUTION SO THAT EXPANSION OF SAIDGAS PRODUCES ROTATION OF SAID VANES, SAID GAS HAVING A SUFFICIENTLY HIGHTEMPERATURE TO CONVERT SAID SALT SOLUTION TO A LIQUID SALT; A RESERVOIRFOR SAID SALT SOLUTION; MEANS INCLUDING A PUMP FOR CIRCULATING THE SALTSOLUTION FROM THE RESERVOIR TO THE INTERIOR OF SAID CASING TO REPLENISHSAID LIQUID PISTON AND FOR RETURNING EXCESS SOLUTION TO SAID RESERVOIR;FIG -01 AND MEANS FOR EXHAUSTING SAID GAS FROM BETWEEN SAID SUCESSIVEPAIRS OF SAID VANES UPON THE EXPANSION THEREOF AND THE PERFORMANCE OFWORK THEREBY ON SAID VANES.